Conventional sandblast photoresists are processed into an imaged mask and then coated with a liquid adhesive composition. These imaged masks generally have mask areas and void areas which will ultimately protect and expose respectively in underlying target surface in a sandblast etching process. Conventional sandblast application operations generally attempt to apply the liquid adhesive only to the mask area which are generally raised with respect to the void areas of the photoresist. A standard application method employs a contact-type role coater which attempts to only contact the raised mask areas of the photoresist. Unfortunately, this mechanical coating does not produce adequate results. Some adhesive is invariably deposited into the void areas of the resist, and subsequently, in the blasting process, this layer of adhesive will slightly impede the blast and leave a surface defect on the etched area of the object. Alternatively, some of the mask areas can also be missed completely or can be given too little adhesive coating. This can result in blow offs of a portion or all of the photoresist during blasting which will ruin an object.
Conventional photoresists for sandblasting are described in VanIseghem, U.S. Pat. No. 4,764,449, Goto et al., U.S. Pat. No. 4,430,416, and Nakamura et al., U.S. Pat. Nos. 4,456,680 and 4,587,186. These references generally discloses the use of photoresist masks which are formed as a photoresist mask laminate away from the target surface and which are then applied to the target surface using an adhesive. The adhesive is generally applied after the imaging and developing of the photoresist mask has been completed. The application of the adhesive is generally not described in any great detail, but is usually applied as described above with some contact-type adhesive applicator or by brushing or spraying.
To form an adherable photoresist, the laminate is exposed to light through a positive image plate. The plate is removed and the photosensitive area is developed to reveal a negative photoresist. A layer of adhesive may then be applied to the developed resist and the laminate comprising the membrane support layer, photoresist layer and adhesive layer is then applied to the surface to be etched or abraded. Careful adhesive application is required to ensure that the adhesive contacts only to the photoresist layer or the adhesive itself may in effect form a further photoresist mask.
Goto et al. discloses sandblast resists which have a minimal tack or adhesion to a target surface. These resists are therefore coated with an additional adhesive to firmly anchor the resist onto the target surface. This reference indicates that the adhesive layer is applied by brush or spray after the resist is formed.
The Nakamura references are directed to photoresist masks for sandblasting comprising a support film layer, a retainer film layer of a water insoluble cellulose derivative and an adhesive, photoresist layer of a pattern mask. The mask is prepared from a liquid photopolymerizable composition layer which is exposed in a pattern using a positive image. Upon exposure and development, the liquid photopolymerizable composition photohardens to form an adhesive photoresist layer. This technology is of limited usefulness as the pre-exposed photosensitive laminate comprises a liquid layer which must be handled with care. Therefore, the exposed photosensitive laminate cannot be shipped for use and exposure by shops or users other than a producer of the laminate itself. Thus, small custom manufacturers of photoresists and do-it-yourselfers are effectively precluded from using this self-adhesive photoresist.
Photoresists are commonly used and valuable industrial materials. Their introduction has greatly reduced processing costs and labor required to form chemically etched and physically abraded surface patterns in articles such as glassware, grave stones, and other decorated surfaces. However, the photoresists and processes for forming these photoresists thus far developed have been of limited versatility. Pre-formed and developed photoresists are often fragile in their unexposed and undeveloped state are formed using complex processes, or require separate, expensive adhesive applicators. These developed photoresists are typically used in-house and are not designed for sale to small users and do-it-yourselfers. The capital expenses required to enable one to form these photoresists effectively prevent their manufacture by these end-users.
Therefore, a versatile, photoresist film laminate which can be mass produced and sold as a pre-exposed and developed photoresist or which can be sold in unexposed and undeveloped form to custom manufacturers and do-it-yourselfers is needed. Characteristics which are helpful to form such a versatile photoresist laminate include a photoimageable, pressure sensitive adhesive layer to provide the adhesive only on the desired areas of the photoresist.